We have previously shown that o-bromophenol and 2-bromohydroquinone, metabolites of bromobenzene, are nephrotoxic. Both o-bromophenol and 2-bromohydroquinone are converted to several isomeric GSH conjugates which give rise to covalently bound material in vitro. Moreover, these GSH conjugates cause elevations in BUN levels and cause nephrotoxicity similar to that observed with bromobenzene, o-bromophenol and 2-bromohydroquinone. Inhibition of Gamma-glutamyl transpeptidase inhibited the covalent binding of the GSH conjugates and the nephrotoxicity of 2-bromohydroquinone. 2-BHQ cysteine but not N-acetyl cysteine conjugates were nephrotoxic.